As wireless technology progresses, communications devices are becoming increasingly integrated and sophisticated. As a result, multi-mode wireless devices are routinely available. A multi-mode wireless device is capable of wireless communications using any of two or more RF communications band. Typically, each RF communications band may be associated with its own RF communications protocol. A multi-mode wireless device may be useful because it is a single communications device that may be used with any of multiple communications networks. Additionally, the multi-mode wireless device may be highly integrated, thereby reducing size, cost, or both
FIG. 1 shows a traditional multi-mode wireless communications device 10 according to the prior art. The traditional multi-mode wireless communications device 10 is coupled to an RF antenna 12, which is used for transmitting and receiving wireless signals. The traditional multi-mode wireless communications device 10 includes a traditional multi-mode front-end module 14, a multi-mode filter module 16, and a traditional multi-mode transceiver module 18. The traditional multi-mode transceiver module 18 may be highly integrated by combining RF and digital functions into a single module. As such, the traditional multi-mode transceiver module 18 may provide baseband processing, RF modulation to create RF signals for transmission, low noise amplification for amplifying low level received RF signals, and down conversion. The traditional multi-mode front-end module 14 is coupled between the RF antenna 12 and the multi-mode filter module 16. A first bi-directional RF signal 20, a second bi-directional RF signal 22, and up to and including an MTH bi-directional RF signal 24 may be used to transfer RF information between the RF antenna 12 and the multi-mode filter module 16 through the traditional multi-mode front-end module 14. Each of the bi-directional RF signals 20, 22, 24 may be either single-ended or differential.
The traditional multi-mode front-end module 14 provides a first transmit signal 26, a second transmit signal 28, and up to and including an NTH transmit signal 30 to the multi-mode filter module 16, which provides a first RF receive signal 32, a second RF receive signal 34, and up to and including a PTH RF receive signal 36 to the traditional multi-mode transceiver module 18. The traditional multi-mode transceiver module 18 provides a high band RF transmit signal 38 and a low band RF transmit signal 40 to the traditional multi-mode front-end module 14. Each of the transmit signals 26, 28, 30 and the RF receive signals 32, 34, 36 may be either single-ended or differential.
FIG. 2 shows details of the traditional multi-mode wireless communications device 10 illustrated in FIG. 1 according to the prior art. The traditional multi-mode transceiver module 18 includes an RF switch circuit 42 and a power amplifier (PA) circuit 44. The traditional multi-mode transceiver module 18 includes low noise amplifier (LNA) circuitry 46. The RF switch circuit 42 is coupled between the RF antenna 12 and the multi-mode filter module 16. The bi-directional RF signals 20, 22, 24 may be used to transfer RF information between the RF antenna 12 and the multi-mode filter module 16 through the RF switch circuit 42. Each of the bi-directional RF signals 20, 22, 24 may be associated with one or more RF communications band. During RF operation, in which RF signals are transmitted and received using a selected RF communications band, the RF switch circuit 42 may select one of the bi-directional RF signals 20, 22, 24 that is associated with the selected RF communications band. Therefore, the selected bi-directional RF signal, which is associated with the selected RF communications band, is used to transfer RF information between the RF antenna 12 and the multi-mode filter module 16.
As is known in the art, a duplexer is a special type of RF filter having two non-overlapping passbands and may be used to process a combined bi-directional RF signal as separate RF transmit signal and RF receive signals. One passband is a receive passband and the other passband is a transmit passband. Specifically, a duplexer may be used to receive an RF transmit signal within the transmit passband and provide the bi-directional RF signal based on the RF transmit signal, and may be used to simultaneously receive an RF receive signal embedded in the bi-directional RF signal within the receive passband and extract and provide the RF receive signal. Therefore, each duplexer may be associated with a bi-directional RF signal, an RF receive signal, and an RF transmit signal. In one example of the traditional multi-mode wireless communications device 10, the multi-mode filter module 16 has a duplexer for each of the bi-directional RF signals 20, 22, 24 that corresponds to one of the RF receive signals 32, 34, 36 and to one of the RF transmit signals 26, 28, 30. Additionally, each duplexer is associated with an RF communications band. Therefore, each of the RF receive signals 32, 34, 36 and each of the RF transmit signals 26, 28, 30 is associated with an RF communications band. Typically, a duplexer may include a receive bandpass filter and a transmit bandpass filter. However, some duplexers may include a bandpass filter and a low pass filter, or a bandpass filter and a high pass filter. A passband associated with a low pass filter or a high pass filter is very wide and may be problematic in some situations.
The PA circuit 44 has multiple PAs (not shown), such that each PA receives and amplifies either the high band RF transmit signal 38 or the low band RF transmit signal 40 to provide at least one of the RF transmit signals 26, 28, 30. The LNA circuitry 46 has multiple LNAs (not shown), such that each LNA receives and amplifies one of the RF receive signals 32, 34, 36. Therefore, each LNA is associated with one of the RF communications bands. Such an arrangement presents several challenges as presented below.
In systems that support large numbers of RF communications bands, the LNA circuitry 46 has a corresponding large number of LNAs, thereby increasing the complexity and cost of the traditional multi-mode transceiver module 18. Further, each LNA may have associated impedance matching circuitry, thereby further increasing cost and complexity. Each time the traditional multi-mode wireless communications device 10 is revised to support an additional RF communications band, the traditional multi-mode transceiver module 18 must be revised to add an additional LNA and then re-qualified, which is time consuming and costly. If a single traditional multi-mode transceiver module 18 design is used in several different wireless communications device designs, unused LNAs and matching circuits add to the overhead of such designs. Since the RF receive signals 32, 34, 36 traverse two separate modules, namely the multi-mode filter module 16 and the traditional multi-mode transceiver module 18, several signal integrity challenges may exist. First, controlling electrical lengths of signal paths associated with the RF receive signals 32, 34, 36 may by difficult or impossible. As such, RF performance may be compromised. Large numbers of signal paths traversing two separate modules may increase susceptibility to noise, other electrical disturbances, or the like. If the traditional multi-mode wireless communications device 10 is a cell phone or other low cost communications device, the traditional multi-mode transceiver module 18 and the multi-mode filter module 16 may have to be constructed using low cost substrates, which may prohibit the use of high impedance RF lines. Low impedance RF lines on low cost substrates may be lossy, difficult to produce to maintain proper impedances, or both. Thus, there is a need to reduce the shortcomings associated with large numbers of LNAs on a multi-mode transceiver module, to facilitate use of high impedance nodes between RF filters and LNAs, and to reduce or eliminate the shortcomings of routing large numbers of RF receive signals between multiple modules.